The present invention relates to an immersion cooling system and, more particularly, to a liquid coolant circulating system thereof.
FIG. 11 shows a conventional coolant circulating system. This is a system for circulating and supplying a liquid coolant to an object to be cooled such as a liquid-cooled electronic part. In FIG. 11, reference numeral 1 denotes a buffer tank for absorbing a variation in volume of a coolant 2 caused by a change in temperature; 3, a discharge pump for supplying the coolant 2 in the buffer tank 1 to an object 5 to be cooled such as an electronic part through a pipe 4; 6, a heat exchanger for cooling the coolant 2 which is heated by cooling the object 5 such as an electronic part to a predetermined temperature and returning the coolant to the buffer tank 1; and 7a, a cooling tank in which the object 5 is incorporated. Note that a constant flow rate valve for obtaining a liquid coolant having a predetermined flow rate may be arranged on the outlet side of the discharge pump 3 as needed.
An operation of the coolant circulating system will be described below. The coolant 2 in the buffer tank 1 is supplied to the cooling tank 7a by a discharge pressure of the discharge pump 3 through the pipe 4 to cool the object 5. Thereafter, the coolant 2 is cooled to a predetermined temperature by the heat exchanger 6 and returned to the buffer tank 1.
FIG. 12 shows another conventional coolant circulating system. In FIG. 12, reference numeral 7b denotes a cooling tank filled with an insulating liquid coolant 2. In the coolant circulating system with this arrangement, an object 5 to be cooled, such as an electronic part, is immersed in the insulating liquid coolant 2 and cooled by boiling the coolant 2. Although this insulating liquid coolant 2 is circulated from the buffer tank 1 to the buffer tank 1 through a pipe 4, the cooling tank 7b, and a heat exchanger 6, by the discharge pressure of a discharge pump 3, the insulating liquid coolant 2, the temperature of which rises, can be cooled to a predetermined temperature by the heat exchanger 6. Note that a cooling scheme using a nucleate boiling scheme is used as a cooling scheme in the cooling tank 7b to increase a cooling efficiency.
In the conventional liquid coolant circulating system described above, however, since only the discharge pump 3 is used as a means for circulating the coolant 2, the discharge pump 3 having a high discharge pressure must be used.
In the coolant circulating system shown in FIG. 12, a circulating system consists of only the discharge pump 3. For this reason, a so-called return pressure of a coolant path extending from the outlet of the coolant tank 7b to the buffer tank 1 through the heat exchanger 6 is charged on the coolant in the coolant tank 7b. As a result, since the boiling point of a coolant in the cooling tank 7b rises, boiling is not promoted, and a sufficient cooling effect cannot be obtained. In addition, since a pressure charged on the flow path is also increased, the withstanding pressure of the cooling tank 7a, the heat exchanger 6 and the like constituting the flow path must be excessively increased.